EP2017383A2 - Method for manufacturing a web of fibrous material - Google Patents

Abstract

The device has a head box delivering suspension jet (18) and has a head box nozzle (10) The head box nozzle is provided such that a change of an outlet slot height by an amount of 1 millimeter measured perpendicular to the inner side of a lower lip (14), changes the beam launch angle between the suspension jet and the inner side of the lower lip by more than 0.1 degree. A body is provided for feeding or withdrawing a preset volume.

Description

The invention relates to a device for producing a fibrous web, in particular paper or board web, comprising a headbox delivering a headbox, which comprises a headbox whose nozzle space is delimited by a lower lip and an opposite upper lip or aperture and two opposing side walls, and For generating the suspension jet having an exit slit.

To keep the beam launch angle constant, the lower lip board has hitherto been dimensioned relatively large, whereby it was regularly larger than twice the exit gap height for this purpose. Primarily due to this geometry, the usual headbox nozzles showed no appreciable dependence of the jet launch angle on the exit gap height.

However, such a nozzle geometry, in particular such a large lower lip board now brings the disadvantage of a pronounced two-sidedness with respect to the sheet structure with it. The lower lip side of the paper differs significantly from the upper lip or diaphragm side, which leads to a reduced dimensional stability of the sheet, in particular with copy paper during the copying process.

In the course of the development of nozzle concepts, which form a much more symmetrical leaf structure, however, an increased dependence of the beam launch angle on the lip opening occurs. Characteristic of such nozzles is in particular a lower lip board, which is smaller than twice the exit gap height.

Fig. 1 shows in a schematic partial representation of such a nearly symmetrical headbox 10. The given in the usual headboxes of paper or board machines using such a nearly symmetrical headbox increased dependence of the beam launch angle β from the exit slit height s and the lower lip board I results from the Fig. 2 ,

As based on the Fig. 1 can be seen, the headbox 10 has a nozzle chamber 12, which is bounded by a lower lip 14 and an opposite upper lip or orifice 16 and two opposing side walls (not shown). It is also provided with an outlet gap 20 for producing the suspension jet 18. The exit gap height is denoted by "S" and the lower lip board opposite to the upper lip 16 by "I".

In the diagram according to Fig. 2 the beam launch angle β is shown above the lower lip board I for different exit gap heights s. The direction of increasing exit slit height s is indicated by the arrow 22.

Thereafter results for smaller lower lip boards I and larger exit slit heights s each have a larger beam launch angle β. In the paper machines known so far, there is a clear dependence of the beam deflection of the exit slit height or lip opening and the lower lip board, when a nearly symmetrical headbox 10 of in Fig. 1 reproduced type with a lower lip board I <2 · s is used.

During operation, this can lead to considerable disturbances in the optimization of the fiber orientation transverse profile and a variation of the exit gap height in the blade.

Thus, a preferably local change of the exit slit height for optimizing the fiber orientation transverse profile is critical, since in particular local adjustments the exit gap height directly bring local changes in the beam launch angle. A new ratio of lower lip board I and exit slit height s changes the bullet geometry, in particular the Strahlauftreffgeometrie or the Strahlauftreffpunkt and can thus lead to possible leaf disturbances. An on the machine width constant insertion geometry of the suspension jet delivered from the headbox into the sheet forming unit is no longer given.

The problems described here are not acceptable at an industrial production facility.

From the EP-B-0 857 816 A headbox is already known in which edge flows are fed to the edge regions of the headbox via edge feed arrangements of a connecting profiling system.

Also from the EP-A-0 445 564 It is already known to set the flow rate at the lateral edges of the headbox nozzle either higher than in the central nozzle area.

At one of the EP-B-0 353 255 known headbox secondary fluid flows are laterally injected at an angle relative to the primary suspension flow.

At one of the DE 35 38 466 C2 known headbox material flows are supplied at the edge varies relative to the main flow of material to influence the fiber orientation accordingly.

The invention has for its object to provide an improved device of the type mentioned, in which the aforementioned problems are eliminated. In particular, it should be ensured that the two negative effects mentioned above are minimized or completely compensated for and that all the advantages of a symmetrical headbox can be utilized.

This object is achieved by the features of claim 1.

It is therefore an apparatus for producing a fibrous web, in particular paper or board web, specified with a suspension jet supplying headbox, which includes a headbox, the nozzle space is bounded by a lower lip and an opposite upper lip or orifice and two opposing side walls, and which has an outlet gap for generating the suspension jet. In this case, the headbox nozzle is such that changes in the measured perpendicular to the inside of the lower lip exit slit height by an amount of 1 mm, the jet discharge angle between the suspension jet and the inside of the lower lip by more than 0.1 °. A device is provided for feeding and / or withdrawing a respective predeterminable volume flow into or out of the two lateral edge regions of the nozzle chamber. In addition, a device for repositioning of the headbox in response to the respective exit slit height is provided to the extent possible to maintain the Strahlauftreffgeometrie as far as possible.

The device according to the invention thus comprises a headbox whose nozzle can be referred to as at least substantially symmetrical. According to the invention, means are also provided by which the undesirable side effects previously encountered in connection with such at least substantially symmetrical headbox nozzles, in particular the strong dependence of the jet launching angle on the exit gap height, etc., are at least substantially compensated. The optimization of the formation transverse profile can now take place independently of the local beam launch angle using an at least approximately symmetrical headbox nozzle. The jet injection conditions in the sheet forming unit are thus constant over the full machine width. In addition, a correspondingly regulated repositioning of the headbox ensures with at least substantially symmetrical headbox nozzle, regardless of changes in the exit slit height constant jet injection conditions. A manual adjustment is not required. It is thus ensured a sufficiently accurate and timely to change the exit slit height or lip opening performed repositioning of the headbox.

Preferably, the lower lip of the headbox nozzle in the region of the outlet gap in a direction parallel to the inside of the lower lip in the exit slit region with respect to the upper lip or aperture at most by an amount which is less than twice the exit slit height measured perpendicular to the inside of the lower lip. Thus, it is also in the present case again at least an essentially symmetrical headbox.

In principle, such a headbox nozzle can be used in which the lower lip does not protrude with respect to the upper lip. The bottom lip and the upper lip of the headbox nozzle can therefore be at least substantially flush in the outlet gap region, for example.

According to an expedient practical embodiment of the device according to the invention, the feed and / or discharge device is designed so that the respective predetermined volume flows are fed into or withdrawn from a respective edge column immediately prior to entry into the nozzle space of the headbox nozzle.

It is advantageous if the headbox for repositioning is at least pivotable. In this case, the headbox is preferably pivotable about an axis extending in the transverse direction.

Alternatively or additionally, the headbox for repositioning can also be translationally displaceable. He is preferably horizontally and / or vertically displaceable.

In a preferred practical embodiment, the headbox for repositioning about the axis of a provided after the headbox forming device is pivotable and displaceable in the vertical and / or horizontal direction. The forming device may in this case comprise at least one forming roller or a forming shoe.

It is particularly advantageous if, in order to influence the jet launch angle between the suspension jet and the inside of the lower lip of the headbox nozzle, the board of the lower lip of the headbox nozzle is variably adjustable with respect to the upper lip.

The device preferably comprises a particularly electronic control device, via which the repositioning of the headbox in dependence on the exit gap height and / or the ratio of lower lip board I and exit gap height s, if the lower lip board I is variable, automatically controlled and / or regulated.

The control device can in particular be connected to a device for measuring the exit slit height, a device for measuring the lower lip board I, a device for detecting the headbox position and an adjusting device for positioning the headbox.

Here, a preferred practical embodiment of the device according to the invention is characterized in that the control device calculates a desired position of the headbox based on the measured exit slit height and / or the calculated ratio of lower lip board I and exit slit height s, this target position with the measured actual position the headbox compares and depending on the comparison result optionally outputs a corresponding correction signal to the adjusting device.

According to a preferred embodiment, by means of the control device, a respective change in the outlet gap height caused by the change in the Beam launch angle or the Strahlauftreffpunkts at least substantially compensated by a corresponding repositioning of the headbox and / or a corresponding adjustment of the lower lip board. For this purpose, in particular corresponding control circuits can be provided.

It is also particularly advantageous if the control device for the automatic control and / or regulation of the fiber orientation transverse profile of the fibrous web is connected to the feed and / or discharge device. The relevant edge-side volume flows can therefore be controlled and / or regulated accordingly to optimize the fiber orientation transverse profile.

The control device can expediently be assigned to a process control system. Of course, the controller can also find their use in a manual operation.

Fig. 1

eine schematische Teildarstellung einer zumindest im Wesentlichen symmetrischen Stoffauflaufdüse;

Fig. 2

ein Diagramm, in dem die bei den bisher üblichen Stoffaufläufen gegebene erhöhte Abhängigkeit des Strahlabschusswinkels von der Austrittsspalthöhe und dem Unterlippenvorstand hervorgeht;

Fig. 3

eine teilweise geschnittene Draufsicht eines Stoffauflaufs mit einer zumindest im Wesentlichen symmetrischen Stoffauflaufdüse mit Randeinspeisung; und

Fig.4

eine schematische Teildarstellung einer beispielhaften Ausführungsform einer erfindungsgemäßen Vorrichtung mit einem eine zumindest im Wesentlichen symmetrische Stoffauflaufdüse gemäß den Fig. 1 und 2 umfassenden Stoffauflauf.

The invention will be explained in more detail below with reference to exemplary embodiments with reference to the drawing; in this show:

Fig. 1

a schematic partial view of an at least substantially symmetrical headbox nozzle;

Fig. 2

a diagram in which given in the usual headboxes increased dependence of the beam launch angle of the exit slit height and the lower lip board is apparent;

Fig. 3

a partially sectioned plan view of a headbox with an at least substantially symmetrical headbox with Randeinspeisung; and

Figure 4

a schematic partial view of an exemplary embodiment of a device according to the invention with an at least substantially symmetrical headbox according to the Fig. 1 and 2 comprehensive headbox.

The Indian Fig. 3 The headbox 24 shown comprises a multiple distributor 28 fed with pulp suspension via a transverse distributor 26, a compensation chamber 30, a turbulence generator 32 and an at least substantially symmetrical headbox nozzle 10 which has already been described in connection with FIG Fig. 1 described type for generating a suspension jet 18th

As already mentioned, the nozzle chamber 12 (see also Fig. 1 ) of the headbox 10 by a lower lip 14 and one of these opposite upper lip or aperture 16 and two mutually opposite side walls 34, 36 limited. To produce the suspension jet 18, the headbox nozzle 10 has an outlet gap 20.

In this case, the headbox 10 is such that changes in the measured perpendicular to the inside of the lower lip 14 outlet slit height s by an amount of 1 mm, the beam discharge angle β between the suspension jet 18 and the inside of the lower lip 14 by more than 0.1 ° , It is therefore a headbox 24 with an at least substantially symmetrical headbox 10 with edge feed.

In this case, the headbox 10 may in particular also be such that the lower lip 14 (see also again Fig. 1 ) in the region of the exit slit 20 in a direction parallel to the inside of the lower lip 14 in the exit slit region X viewed with respect to the upper lip or aperture 16 by a maximum amount I projecting smaller than twice perpendicular to the inside of the lower lip 14 measured exit slit height s. The amount I is referred to in professional circles as the lower lip board.

The lower lip 14 and the upper lip 12 of the headbox nozzle 10 can also be at least substantially flush in the outlet gap region, for example. The lower lip board I then becomes "0" in this case.

As based on the Fig. 3 can be seen, in addition, a means 38 for feeding and / or for subtracting a respective predetermined volume flow in or out of the two lateral edge regions 40, 42 of the nozzle chamber 12 is provided. In this case, this feed and / or outlet device 38 can be embodied in particular such that the relevant specifiable volume flows are fed into or withdrawn from a respective edge gap immediately before entry into the nozzle chamber 12 of the headbox nozzle 10.

As based on the Fig. 3 can be seen, the feed and / or discharge device 38 may include lateral supply and / or discharge lines 44, in each of which at least one adjustable valve, in particular control valve, may be used. In the present embodiment, these lines 44 are connected to the transverse distributor 26. Instead of stock suspension, for example, dilution water or the like can be supplied to at least one of the two lateral edge regions.

As already mentioned, in the Fig. 3 reproduced headbox 24 in particular a headbox 10 of the Fig. 1 own type described. It is therefore an at least substantially symmetrical headbox 10.

Fig. 4 shows a schematic partial representation of an exemplary embodiment of a device 48 according to the invention for producing a fibrous web, which may be in particular a paper or board web. In this case, this device 48 comprises a suspension jet 18 delivering headbox 24 in the Fig. 1 and 3 described type and also also already with reference to the Fig. 3 explained feed-in and / or discharge device 38.

In addition, this device 48 for influencing the beam launch angle β (see also FIG Fig. 1 ) between the suspension jet 18th and the inside of the lower lip 14, a device 48 for repositioning the headbox 24 in response to the respective exit slit height s.

As already mentioned, the feed and / or discharge device 38 (cf. Fig. 3 ) be designed in particular so that the respective predeterminable edge-side volume flows are fed immediately before entry into the nozzle chamber 12 of the headbox 10 in a respective edge column or withdrawn from this.

The headbox 24 may be pivotable for repositioning, for example. It may, for example, be pivotable about a transversely extending lower axis 50.

Alternatively or additionally, the headbox 24 for repositioning, however, for example, be translationally displaced. In this case, it is preferably at least horizontally and / or vertically displaceable.

As based on the Fig. 4 1, the suspension jet 18 is introduced into an inlet gap 58 formed between two screens 52, 54 in the region of a forming roller 56. In this case, in the region of this inlet gap 58, the wire 52 is guided around the forming roller 56 and the wire 54 around a further roller 60.

For repositioning, the headbox 24 may, for example, be pivotable about the axis of the forming roller 56 and advantageously additionally displaceable in the vertical and / or horizontal direction.

For influencing the beam launch angle β (see also again Fig. 1 ) between the suspension jet 18 and the inside of the lower lip 14 of the headbox 24, in particular, the board I of the lower lip 14 of the headbox 10 with respect to the upper lip or aperture 16 may be variably adjustable.

As based on the Fig. 4 can be seen, the device 10 also includes a particular electronic control device 62, via which the Nachpositionierung the headbox in dependence on the exit slit height s (see also Fig. 1 ) and / or the ratio of lower lip board I and exit slit height s, if the lower lip board I is variable, is automatically controlled and / or regulated.

In this case, the control device 52 may in particular be connected to a device 64 for measuring the outlet gap height s, a means for measuring the lower lip board I, a device 82 for detecting the headbox position and an adjusting device 68 for positioning the headbox 24.

As based on the Fig. 4 can be seen, the controller 62, for example, a programmable logic circuit 70 for calculating the desired position of the headbox 24 based on the measured exit slit height s, a comparison circuit 72 for comparing the calculated target position with the measured actual position of the headbox 24 and a controller 74, which optionally outputs a corresponding control value or correction signal to the adjusting device 68 as a function of the result of the comparison. The control device 62 can thus be designed in particular so that it calculates the desired position of the headbox 24 on the basis of the measured exit slit height s and / or the calculated ratio of lower lip board I and exit slit height s, this desired position with the measured actual position of the headbox 24 compares and, depending on the comparison result optionally outputs a corresponding correction signal to the adjusting device 68.

The headbox position detection means 66 may comprise, for example, an angle encoder on a drive shaft associated with the actuator 68. The adjusting device 68 comprises z. B. a positioning, the over the controller 62 and the controller 74 can be controlled to compensate for beam launch angle changes.

As based on the Fig. 4 can be seen, results from the control device 62, the corresponding measuring devices 64, 66 and the adjusting device 68, a corresponding control loop for repositioning the headbox 24 after a respective change in the exit slit height or lip opening s, for example, to maintain a predetermined beam launch angle.

Thus, by means of the control device 62, in particular a respective change of the jet launch angle β or of the jet impact point caused by a change in the exit slit height s can be at least substantially compensated by a corresponding repositioning of the headbox 24 and / or a corresponding readjustment of the lower lip board I.

In particular, for automatic control and / or regulation of the fiber orientation transverse profile of the fibrous web, the control device 62 may in particular also be connected to the feed and / or discharge device 38.

The control device 62 can be assigned to a process control system of the relevant production or paper machine.

Thus, an at least substantially symmetrical headbox nozzle 10 is combined with a feed and / or take-off device 38 for optimizing the fiber orientation transverse profile. In this case, immediately before the entry of the headbox suspension stream into the nozzle chamber 12 of the headbox nozzle 10, a defined volume flow in the marginal column off or fed, whereby cross flows are caused in the nozzle chamber 12 and the fiber orientation is influenced accordingly.

There is thus no specific profiling of the exit gap 20 for optimizing the fiber formation (TSO) longer required.

In addition, the at least substantially symmetrical headbox 10 is combined with a dependent of the exit slit height or lip opening s subsequent positioning of the headbox 24. In this case, the setpoint position of the headbox 24 can be calculated via the control device 62 on the basis of the measured outlet slit height s. After a comparison of this desired position with the also detected actual position of the headbox 24, if necessary, a corresponding signal for correcting the headbox position to the particular one positioning drive comprehensive adjusting device 68 are given.

For repositioning of the headbox 24, this may for example be pivotable about an axis 50. In principle, however, any other variants for repositioning are conceivable. For example, a pivoting movement about the forming roller 56 in combination with a horizontal and / or vertical displacement is possible. It is for example also a correction by a change of the lower lip board I conceivable. Thus, the beam launch angle α can also be significantly influenced. Although this may also affect the leaf structure two-sidedness, the necessary adjustment paths are minimal, so that the influence on the two-sidedness in practice is negligible.

As can be seen in particular from the Fig. 4 results, among other things, a control loop for repositioning the headbox 24 after a change in the gap exit height or lip opening s, according to the invention a control engineering coupling between the exit slit height or lip opening s and the positioning of the headbox 24 is possible.

LIST OF REFERENCE NUMBERS

10

headbox

12

nozzle chamber

14

bottom lip

16

Upper lip, aperture

18

suspension jet

20

exit slit

22

arrow

24

headbox

26

Querverteiler

28

Manifold

30

compensation chamber

32

turbulence generator

34

Side wall

36

Side wall

38

Feed and / or discharge device

40

border area

42

border area

44

Supply and / or discharge

46

Valve, control valve

48

Device for repositioning

50

axis

52

scree

54

scree

56

forming roll

58

inlet gap

60

roller

62

control

64

Device for measuring the exit gap height

66

Device for detecting the headbox position

68

setting device

70

Programmable logic circuit

72

comparison circuit

I

Lower lip Board

s

Exit slit height

X

direction

β

Beam launch angle

Claims (15)

Apparatus (48) for producing a fibrous web, in particular paper or board web, comprising a headbox (24) which delivers a jet stream (18) and comprises a headbox nozzle (10), the nozzle chamber (12) of which is formed by a lower lip (14) and one of these opposite upper lip (16) and two opposite side walls (34, 36) is limited, and for generating the suspension jet (18) has an outlet gap (20),
characterized,
that the headbox nozzle (10) is such that when the outlet gap height (s) measured perpendicularly to the inside of the lower lip (14) changes by an amount of 1 mm, the jet discharge angle (β) between the suspension jet (18) and the inside of the jet Lower lip (14) changes by more than 0.1 °, that means (38) for feeding and / or for subtracting a respective vorgebaren volume flow in or from the two lateral edge regions (40, 42) of the nozzle chamber (12) is provided and in that, for the purpose of keeping the jet impact geometry as constant as possible, provision is made for a device (48) for repositioning the head box (24) as a function of the respective outlet gap height (s). Device according to claim 1,
characterized,
in that the bottom lip (14) of the headbox nozzle (10) in the region of the outlet gap (20) in a to the inside of the lower lip (14) in Outlet gap area parallel direction (X) viewed with respect to the upper lip (16) protrudes a maximum amount (I) which is less than twice the measured perpendicular to the inside of the lower lip exit gap height (s). Apparatus according to claim 1 or 2,
characterized,
in that the lower lip (14) and the upper lip (12) of the headbox nozzle (10) are at least substantially flush in the outlet gap region. Device according to one of the preceding claims,
characterized,
that the supply and / or removal device (38) is constructed so that the predetermined volume flow in question are fed immediately before entry into the nozzle chamber (12) of the headbox nozzle (10) in a respective edge column or withdrawn from the latter. Device according to one of the preceding claims,
characterized,
that the headbox (24) for repositioning at least pivotally. Device according to claim 5,
characterized,
in that the headbox (24) is pivotable about a transversely extending axis (50). Device according to one of the preceding claims,
characterized,
that the headbox (24) for repositioning at least translationally displaceable. Device according to claim 7,
characterized,
that the headbox (24) for repositioning is at least horizontally and / or vertically displaceable. Device according to one of the preceding claims,
characterized,
that it comprises a forming device (56) following the headbox (24) and
in that the headbox (24) is pivotable about the axis of the former (56) and displaceable in the vertical and / or horizontal direction for subsequent positioning. Device according to one of the preceding claims,
characterized,
in that for influencing the jet launch angle (β) between the suspension jet (18) and the inside of the lower lip (14) of the headbox nozzle (24), the board (I) of the lower lip (14) of the headbox nozzle (10) is variably adjustable with respect to the upper lip (16) is. Device according to one of the preceding claims,
characterized,
in that it comprises a particularly electronic control device (62) via which the repositioning of the headbox (24) in dependence on the exit slit height (s) and / or the calculated ratio of lower lip board (I) and exit slit height (s), if the lower lip board (I ) is variable, is automatically controllable and / or regulated. Device according to one of the preceding claims,
characterized,
in that the control device (62) is provided with means (64) for measuring the exit slit height (s), means for measuring the lower lip board (I), means (66) for detecting headbox position and adjusting means (68) for positioning the headbox Headbox is connected. Device according to claim 12,
characterized,
that the control device (62) based on the measured discharge gap height (s) is a target position of the head box (24) is calculated, compares the target position with the measured actual position of the headbox (24) and in dependence on the comparison result, if necessary, a corresponding correction signal to the adjusting device (68). Device according to one of the preceding claims,
characterized,
in that by the control device (62) a respective change of the jet launching angle (β) or of the jet impact point caused by a change of the outlet gap height (s) by a corresponding repositioning of the head box (24) and / or a corresponding adjustment of the lower lip board (I) at least in the Is substantially compensated. Device according to one of the preceding claims,
characterized,
that the control means (62) for the automatic control and / or regulation of the fiber orientation transverse profile of the fibrous web with the supply and / or removal device (38).

Images